When you put your camera to the mount make it tight as you can.
When you attach the mount to the bars make it as tight as you can,
I add strips from an inner tube to make it even more stable, be careful
you don't end up covering some important buttons. This will help but
not completely eliminate shakes from big/multiple bumps.

Fujifilm XP50 pocket camera mounted with a Fotopro on the bars and
2 inner tube strips:

http://www.youtube.com/watch?v=uEwthddqM9U

ConoturGPS mounted on the bars with just stips of an old tube:
http://www.youtube.com/watch?v=aJA9SXNTsd8




HOMEMADE CONTOUR MOUNT1 by 1nterceptor, on Flickr